The present invention relates to a method and a device for widening tubular organs in general and to a method and a device for widening arteries in particular.
Devices and methods for widening tube shaped organs, in general and in the human body, in particular, are known in the art.
U.S. Pat. No. 5,716,410, to Wang et al, is directed to a catheter for vascular use. The catheter includes a directing mechanism and an inflatable balloon at the tip. The tip also includes a temporary stent, made of thermoplastic material. The catheter is inserted into the body of the patient, via a wide surface artery and the operator directs the catheter toward the destination location. When the tip is positioned at the destination location, then the operator pumps fluid to the balloon, via a tube, running along the catheter and starts inflating the balloon.
Reference is now made to FIG. 2, provided by Wang et al as FIG. 1, which is an illustration of a catheter, known in the art.
At the same time, the thermoplastic stent is heated, thereby unlocking its shape. The balloon, as it inflates, applies circumferencial pressure on the stent and the tubular organ, thereby forcing them to extend. Accordingly, the circumference of the tubular organ becomes larger. When the balloon brings the thermoplastic stent to the destination diameter, then the thermoplastic stent is cooled, thereby fixing its shape at a larger diameter, where it supports the tubular organ at an enlarged position.
Then, the operator reduces the pressure within the balloon, which in turn deflates and becomes smaller than the enlarged circumference of the tubular organ. The thermoplastic stent is then kept within the tubular organ for a time period which may range from a few minutes to as long as a week. Finally, the thermoplastic stent is reheated, thereby unlocking its shape, and enabling its removal from the body of the patient.
It will be appreciated by those skilled in the art, that a balloon is often longer than the segment to be treated. Hence, the inflatable portion of the balloon extends beyond the desired segments to healthy segments, and can cause damage thereto.
Furthermore, when a balloon is inflated inside a blood vessel, it occludes the blood flow distally and becomes a full barrier for any blood flow therein. It will be appreciated by those skilled in the art that many blood vessel related balloon treatments are performed in coronary arteries. Accordingly, such a procedure, while blocking blood flow through the treated blood vessel, may cause ischemia or even cardiac arrest.
The balloon blocks the blood flow both in the axial (through the blood vessel) and radial directions blocking branches.
The complete obstruction, a balloon related treatment is usually limited to one or two minutes of inflation, since the patient can not tolerate long time inflations, because of severe pain and chest discomfort, due to ischemia.
It will be appreciated by those skilled in the art that a blood vessel is generally a flexible organ. This fact, combined with the short time period in which a balloon expands the circumference of the blood vessel, (as much as 40% of the cases) causes the balloon treated blood vessel to assume its original size (recoil) immediately, or within few months shortly after the treatment.
A stent is generally an element, which is inserted into the tubular organ with the aid of a catheter. The initial shape of a stent is of an elongated cylinder, having a diameter, which is smaller than the narrowed section of the tubular organ, through which it has to pass. At the beginning of the treatment, the stent is positioned in the stenosed segment.
Then, the circumference of the stent is widened, by various methods, known in the art. One of these methods includes inserting a balloon into the stent and applying pressure by inflating it therewith. Accordingly, the stent widens, thereby applying pressure on the narrowed blood vessel. As a result, the stent widens the cross section of the diseased segment.
Finally, the balloon is deflated and is removed from the stent, which remains in its widened position, forcing the widened blood vessel to remain at its new state. Afterwards, the stent is covered by local tissue and is anchored thereto. This poses a disadvantage in the usage of a stent since such a stent can not be removed. A stent is an alien element within a living organism, which might produce thrombus in it.
In many cases (15%-40%) instant stenosis occurs. The mechanism of this narrowing is intimal proliferation thereby causing a new blockage at the same location. It is known by those skilled in the art that sometimes, such a reoccurring blockage is difficult to treat and in some cases, surgery is needed, to remove and replace the clogged section.
In some instances the stent may be lost and migrate distally in the coronary artery, or sometimes in the aorta and its branches. The stent also can be stuck.
Shape memory effect (SME) is a phenomena, in shape memory alloys (SMA) of a reversible transition from one solid phase into the other (i.e., from Martensite into Austenite or from Austenite to Martensite). Heating the alloy causes the transition from Martensite into Austenite. Cooling the alloy causes the reverse transition, from Austenite into Martensite. NiTi alloys are examples for such shape memory alloys.
Martensite and Austenite are two solid state phases, which are typical for alloys. Each of these phases is characterized in a certain crystalline structure.
Basically there are two types of shape memory effects. The first type is called the one way shape memory effect (OWSM), where the material transits from one of the above phase states to the other, only once. The second type is called the two-way shape memory effect (TWSM), where the material transits from one of the phase states to the other and back in a reversible process.
Shape memory alloys, such as Nixe2x80x94Ti, Nixe2x80x94Tixe2x80x94X, Cuxe2x80x94Nixe2x80x94Al, Cuxe2x80x94Znxe2x80x94Al, Fexe2x80x94Mnxe2x80x94Si, Nixe2x80x94Tixe2x80x94Co, Nixe2x80x94Cuxe2x80x94X, Nixe2x80x94Al and the like, are known in the art. These alloys exhibit a shape memory effect. In the Martensite condition, the shape alloy material is relatively flexible and soft, and can be easily deformed. When the material undergoes the transition into an Austenite state, it becomes more rigid, and is able to apply force and generate work, deform and enlarge the cross section of the blood vessel.
U.S. Pat. No. 5,540,713 to Shnepp-Pesch et al, is directed to an apparatus for widening a stenosis in a body cavity, also known as a shape memory stent. Shnepp-Pesch describes a stent made from a shape memory alloy, assuming a first predetermined shape at a first predetermined temperature and second predetermined shape at a second predetermined temperature. When heated from the first temperature to the second one, the shape memory stent changes its shape from a narrow generally cylindrical shape to a wider generally cylindrical shape.
Shnepp-Pesch describe a plurality of shapes which are applicable as shape memory stents. Reference is now made to FIGS. 1A-1H, provided by Shnepp-Pesch et al, as FIGS. 1A, 1B, 2A, 2B, 3A, 3B, 4A and 4B, respectively. These figures describe four shape memory stent structures, each at two states, one narrowed and the other enlarged.
It will be appreciated by those skilled in the art that this stent basically suffers the same disadvantages as any other stent, known in the art, as listed above.
It is an object of the present invention to provide a system for opening and temporarily supporting generally tubular organs, in general and arteries in particular.
It is a further object of the present invention to provide a novel method for temporarily supporting a tubular organ, in general and vascular organs in particular.
In accordance with the present invention, there is thus provided a system for opening and temporarily supporting a section of a generally tubular organ. The system includes a dilation catheter. The dilation catheter includes an integrally connected shape memory catheter tip. The shape memory catheter tip is made of a shape memory alloy, wherein the shape memory catheter tip assumes a first shape at a first temperature and a second shape at a second temperature. It is noted that the shape memory catheter tip is generally hollow, thereby enabling flow of bodily fluid there through.
The system can further include an energy control unit, connected to the dilation catheter, and an energy transfer unit. The energy control unit controls the temperature of the shape memory catheter tip. The energy transfer unit is connected between the shape memory catheter tip and the energy control unit, and generally located within the dilating catheter, for transferring energy there between.
The shape memory catheter tip can include a plurality of shapes. For example, the shape of the shape memory catheter tip can be selected from the list consisting of a generally cylindrical coil, a generally cylindrical mesh, a folded foil and the like. Such a folded foil can include a plurality of openings.
According to one aspect of the invention, the first shape is generally the shape of a cylindrical coil, having a first diameter and wherein the second shape is generally the shape of a cylindrical coil, having a second diameter. According to another aspect of the invention, the first shape is generally the shape of a cylindrical mesh having a first diameter and wherein the second shape is generally the shape of a cylindrical mesh having a second diameter. According to a further aspect of the invention, the first shape is generally the shape of a cylindrically folded foil having a first diameter and wherein the second shape is generally the shape of a cylindrically folded foil having a second diameter.
The energy transfer means can include at least one conduit. Such conduits can include concentric conduits. The temperature control unit can include means for providing temperature-controlled fluid towards the shape memory unit via the energy transfer means. The conduit can be opened in the vicinity of the shape memory catheter tip, thereby releasing temperature controlled fluid in the vicinity of the shape memory catheter tip. The temperature control unit can further be connected electrically to the shape memory unit, thereby electrically heating the shape memory unit from the first temperature to the second temperature.
The energy transfer means can further include an electricity-conducting unit, connected electrically to the shape memory unit. Accordingly, the temperature control unit can include an electric power supply unit, for electrically heating the shape memory unit from the first temperature to the second temperature.
It is noted that the first temperature can be set to be equal or below the temperature of the environment, in which the shape memory catheter tip is placed. The shape memory alloy can be selected from the list consisting of: Nixe2x80x94Ti, Nixe2x80x94Tixe2x80x94X, Cuxe2x80x94Nixe2x80x94Al, Cuxe2x80x94Znxe2x80x94Al, Fexe2x80x94Mnxe2x80x94Si, Nixe2x80x94Tixe2x80x94Co, Nixe2x80x94Cuxe2x80x94X, Nixe2x80x94Al and the like.
For example, the first temperature can be in the range of 5 degrees Celsius and 38 degrees Celsius. Alternatively, the first temperature is in the range of 20 degrees Celsius and 38 degrees Celsius. Similarly, the second temperature can be in the range of 36 degrees Celsius and 65 degrees Celsius. Alternatively, the second temperature is in the range of 36 degrees Celsius and 50 degrees Celsius.
According to another aspect of the invention, the shape memory unit includes a generally cylindrical hollow coil, having an inlet and an outlet and the temperature transfer means includes two conduits. Accordingly, one of the conduits is connected to the inlet of the shape memory unit for introducing the fluid thereto, and the other of the conduits is connected to the outlet, for receiving the fluid therefrom.
According to a further aspect of the invention, the system further includes elastic elements, such as a spring, attached to the shape memory catheter tip having an initial shape, wherein the initial shape (of the elastic elements) is generally similar to the first shape (of the catheter tip). The elastic elements apply force on the shape memory catheter tip so as to deform the shape memory catheter tip to the initial shape. The elastic elements can be attached to the shape memory unit.
The front section of the shape memory catheter tip can be shaped as a guiding front end. Alternatively, the system can further include a guiding unit having a guiding tip, wherein the guiding unit is located within the dilation catheter and extends beyond the shape memory catheter tip. The guiding tip can be operable to move relative to the shape memory catheter tip.
It is noted that according to one aspect of the invention, the first diameter can be smaller than the second diameter. Alternatively, the first diameter can be larger than the second diameter.
The shape memory catheter tip enables flow of bodily fluid in a radial direction and in an axial direction, by having front, rear and side openings.
In accordance with another aspect of the invention, the system can further includes an inflatable balloon. The balloon is operative to inflate, thereby changing the shape memory catheter tip from the first shape into the second shape. According to this aspect, the shape memory catheter tip changes from the second shape to the first shape when heated from the first temperature to the second temperature.
In accordance with a further aspect of the invention, there is provided a method for operating the system including the steps of: inflating the balloon, thereby increasing the diameter of the shape memory catheter tip, deflating the balloon, thereby enabling flow of bodily fluids through the shape memory catheter tip, heating the shape memory catheter tip to a predetermined temperature, thereby moving the shape memory catheter tip to an Austenite state which decreases the diameter of the shape memory catheter tip.
The method can further include a preliminary step of locating the shape memory catheter tip and the balloon in a selected area within a generally tubular organ. The method can further include a further preliminary step of inserting the shape memory catheter tip and the balloon into the body of the patient. Moreover, the method can further include a step of removing the shape memory catheter tip from the selected area.